3 2o PRACTICAL ORGANIC CHEMISTRY Sodium sulphanilate. —Burns with difficulty, leaving a residue of (chiefly) sodium sulphide. Add dil. HCl, and confirm without delay the evolution of H 2 S by means of a filter-paper moistened with lead acetate solution. Typical of salts of the sulphonic acids. Acetone sodium bisulphite. —Almost non-inflammable, leaving a colour-less residue of sodium sulphite and sulphate. Transfer residue to a test-tube, add dil. HCl, warm, and confirm the SO 2 evolved. Cane sugar. —Melts, darkens, then chars, and finally burns, with a marked odour of burnt sugar. Typical of the changes given by mono- and di-saccharides. Tartaric acid and tartrates also swell up, blacken and give an odour resembling burnt sugar. Citrates and lactates also char, and give off odours resembling burnt sugar. A large variety of organic compounds char without melting, e.g., starch, oxamide, sulphonic acids, uric acid, etc. NOTE, (i) Care should be taken to distinguish between a residue of carbon
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